XmlSerializer class in .NET 4.5 uses reflection emit to improve the cold startup time of your application. If you happen to run into any compatibility issues on running your existing .NET 40 applications running on a machine with .NET runtime >= 4...

I've seen quite a lot of people running into the issue where their OWIN startup class is not detected. Here are some of the more common reasons why the OWIN startup class is not detected.
Check if your IIS application pool is in Integrated mode...

Do you happen to see FileLoadException when you try to run a OWIN application (SignalR or WebAPI) on a worker role project with the below message?
System.IO.FileLoadException: Could not load file or assembly 'Microsoft.Owin, Version=2.0.0.0, Culture...

Do you notice that your WCF NetTcp endpoint sharing port with a mexTcp endpoint fails to activate with a AddressAlreadyInUseException on upgrade to .Net 4.5? System.ServiceModel.AddressAlreadyInUseException : There is already a listener on IP endpoint...

In .net 4.5 WCF leveraged the buffer less input stream for scalability benefits. As a result when you try to access the HttpContext.Current.Request.InputStream property you may end up with the below exception, as the InputStream property tries to get...

In order to simply configuration a number of transport property defaults and XmlDictionaryReaderQuotas values were changed in WCF 4.5. For exact details about changes refer this link under topics “ New Transport Default Values ” and “...

Do you see that a WCF service with aspNetCompabitilityEnabled=”true” works fine on a machine with .net framework runtime 4.5, but the same service fails to activate with the below exception on a machine with v4.0 runtime. Here is how you can...

In VS 2012 MVC 4 projects, do you find an empty reference.cs file while adding a service reference to a WCF service using 'Add service reference' dialog?
Here is what you can do about it:
Check if your error tab shows some error like...
Warning...

If you have a WCF service with netHttpBinding/basicHttpsBinding/udpBinding endpoint using the .net 4.5 RC bits and your service fails to activate with this error message on upgrading to .net 4.5 RTM bits, here is what you need to do.
Configuration...